PDF Viewers for Unix, BSD, and Linux

Adobe Reader

ggv

Ghostview (Original)

http://www.cs.wisc.edu/~ghost/gv/index.htm

Ghostview / gv

http://wwwthep.physik.uni-mainz.de/~plass/gv/

Uses Xaw3d.

gpdf

GSview

http://www.cs.wisc.edu/~ghost/gsview/index.htm

Uses GTK+.

kghostview

kpdf

Mgv

Motif front-end to original ghostview.

vpp

http://www.servalys.nl/tex/vpp.html

Just a wrapper around another PDF viewer.

xpdf

http://www.foolabs.com/xpdf/

Other links

LWN: The Grumpy Editor's Guide to PDF Viewers